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Map explanation

This map shows where changes occurred in the relative abundance of the species in Wiltshire between 1995-2000 and 2007-2012, as revealed by the fieldwork for Birds of Wiltshire (Wiltshire Ornithological Society 2007) and the shared fieldwork for Bird Atlas 2007-2011 (BTO 2013) and for Wiltshire Tetrad Atlas 2007-2012.

Key

Relative to average

Nos tetrads

More abundant

0

0%

Equally abundant

0

0%

Less abundant

0

0%

Not surveyed in both periods

Native of an area stretching from south Canada to Central America and the Caribbean, Ruddy Ducks were first introduced to collections in Europe in 1936. Two pairs were brought to Slimbridge in 1948, where they readily bred. By 1963 some 70 unpinioned juveniles had escaped into the wild, establishing successful naturalised populations, initially in Chew Valley Lake in Somerset and the West Midlands, then spreading to other parts of England, Wales and Scotland. The1988-91 Breeding Atlas estimated the population at 570 pairs. By the winter of 1999-2000, Wetland Bird Survey counts were showing a British count of 4565 and the UK population is estimated to have peaked at around 6000 in 2000. Meantime, the species had spread to 19 other European and North African countries including Spain, where it hybridised with the local population of the globally endangered White-headed Duck Oxyura leucocephala. Because of this threat of genetic swamping of an endangered species a control and subsequent eradication programme was launched, which in Britain led to a 90% reduction by 2009 and to possibly no more than 60 individuals in 2012. Ruddy Ducks first appeared in Wiltshire in the late 1960s, but it was not until 1976 that they started to appear annually in gradually increasing numbers. They first bred in the county at Tockenham Reservoir in 1977, though it was 11 years before they were again recorded breeding, at Langford Lakes, in August 1988. From 1990 until 2001, they bred every year, often in two or three different sites. After a hiatus in 2002, they were again recorded breeding for four more years until 2006 when they bred at Coate Water, Corsham and the Cotswold Water Park (CWP). There have been no further breeding records since then. Numbers wintering in the county built up to a maximum of 112 at six separate sites in December 2003. Thereafter numbers began to decline as the eradication programme kicked in, falling to 63 at seven sites in 2005, 33 at six sites in 2006, 12 at three sites in 2009, six at a single site (CWP) in 2012 and finally to just one lingering on at the CWP in 2015.